Study of the function of the living human brain is difficult for all the following reasons,EXCEPT?

Study of the function of the living human brain is difficult for all the following reasons,EXCEPT
A ) it is unethical to induce brain damage in humans for the purpose of research.
B ) brain damage is rarely the same from case to case.
C ) it is difficult to obtain the brain of a person who has suffered brain damage.
D ) researchers have to wait for the natural death of a brain-damaged human to verify the location of the brain damage.
E ) a damaged brain gives us little information about brain structure and function in the living brain.